It is well known that an individual's emotions or mental state can cause physiological changes. Examples of such physiological changes include sweating, changes in respiration, facial movements, fidgeting, changes to blood pressure, and changes to heart rate. Heart-rate related indications of mental state can include a measure of absolute heart rate (HR), heart rate variability (HRV), and blood volume pulse (BVP). An individual's heart rate can be measured in various ways, including using a medical electrocardiograph (EKG) machine, a chest strap with electrodes, a pulse oximeter that clips on a finger, a sphygmomanometer, or by measuring a pressure point on an individual.
A person's mental state can be impacted by many types of external stimuli. One growingly common stimulus is interaction with a computer. People spend an ever-increasing amount of time interacting with computers, and consume a vast amount of computer-delivered media. This interaction can be for many different reasons, such as desire for educational content, entertainment, social media interaction, document creation, and gaming, to name a few.
In some cases, the human-computer interaction can take the form of a person performing a task using a computer and a software tool running on the computer. Examples of such interactions can include filling out a tax form, creating a document, editing a video, and doing one or more of the other activities that a modern computer can perform. The person might find certain activities interesting or even exciting, and might be surprised at how easy it is to perform the activity or activities. The person can become excited, happy, or content as they perform the activities. On the other hand, the person might find some activities difficult to perform, and can become frustrated or even angry with the computer, even though the computer is oblivious to their emotions. In other cases of human-computer interaction, the person can be consuming content or media such as news, pictures, music, or video. A person's mental state can be useful in determining whether or not the person enjoys particular media content.
Currently, tedious methods with limited usefulness are employed to determine users' mental states. For example, users can be surveyed in an attempt to determine their mental state in reaction to a stimulus such as a human-computer interaction. Survey results are often unreliable because the surveys are often done well after the activity was performed, survey participation rates can be low, and many times people do not provide accurate and honest answers to the survey questions. In other cases, people can self-rate media to communicate personal preferences by entering a specific number of stars corresponding to a level of like or dislike. However, these types of subjective evaluations are often neither a reliable nor practical way to evaluate personal response to media. Recommendations based on such methods are imprecise, subjective, unreliable, and are often further subject to problems related to the small number of individuals willing to participate in the evaluations.